From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id D2485C79FAD for ; Wed, 9 Sep 2026 09:15:13 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 56B4210F039; Wed, 9 Sep 2026 09:15:13 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.b="fg8DO+TX"; dkim-atps=neutral Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by gabe.freedesktop.org (Postfix) with ESMTPS id 298D610F037; Wed, 9 Sep 2026 09:15:12 +0000 (UTC) Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id C5560409AC; Wed, 9 Sep 2026 09:15:11 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 011DA1F00A3A; Wed, 9 Sep 2026 09:15:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788945311; bh=gLDyNFD1/RvPm1J7pM+BXHTtKoCe4+PeIOeIYj4a48k=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=fg8DO+TXq2FAIjw+/tsm+bwwrTgwpGh+mNzuJ7O4UdoHaHD6yiw8eJRH2u0ESjl/J zlZzP35cb+q2QJa3haIsH/MC9ErlOJZcoZMLNtn3corFf5U/l7vkjjaVhdGDDIX85c LO0i7xLtkiUMOIyoBEL+Dp0H6ruZamGwo+49KI5pLJ7MraWSD4Oty3ebEUEW+lxV0l vc77Mx+CiKKK2Ogdrr8jlVjPpSKrxK/5cAlcCPm5bJ4dg83+Xl9bLCVmNlGYVUFbYF R2mCqCrL9WPpm2TR09Rpy47aOFgU7xk5ahn94OwRb4sVku91UUgDOqlCBOqQO11LnG cdrT6ZGzIuWJw== From: sashiko-bot@kernel.org Subject: Re: [PATCH v4 02/14] drm/panic: Test address from kmap op for NULL To: "Thomas Zimmermann" Cc: linux-hyperv@vger.kernel.org, dri-devel@lists.freedesktop.org, ojeda@kernel.org, gary@garyguo.net, "Michael S. Tsirkin" , imx@lists.linux.dev, wsa+renesas@sang-engineering.com, "Eugenio Perez" , virtualization@lists.linux.dev, Frank.Li@kernel.org, intel-xe@lists.freedesktop.org, intel-gfx@lists.freedesktop.org In-Reply-To: <20260909085826.64529-3-tzimmermann@suse.de> References: <20260909085826.64529-1-tzimmermann@suse.de> <20260909085826.64529-3-tzimmermann@suse.de> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Wed, 09 Sep 2026 09:15:10 +0000 Message-Id: <20260909091511.011DA1F00A3A@smtp.kernel.org> X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: sashiko-reviews@lists.linux.dev Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" Thank you for your contribution! Sashiko AI review found 1 potential issue(= s) to consider: Pre-existing issues: - [High] Potential NULL pointer dereference in `kmap_local_page_try_from_pa= nic()` due to missing NULL checks for page pointers in `drm_panic_fill_page= ()` and `drm_panic_blit_page()`. -- commit ddaf01e3dc4138e21af0a9818e11a3a8b5244eae Author: Thomas Zimmermann drm/panic: Test address from kmap op for NULL This patch adds a NULL check for the return value of kmap_local_page_try_from_panic() to avoid dereferencing a failed mapping during kernel panic screen rendering. > diff --git a/drivers/gpu/drm/drm_panic.c b/drivers/gpu/drm/drm_panic.c > index ba21df4be3380..d28ce8878e055 100644 > --- a/drivers/gpu/drm/drm_panic.c > +++ b/drivers/gpu/drm/drm_panic.c > @@ -178,6 +178,8 @@ static void drm_panic_write_pixel24_xpage(void *vaddr= , struct page *next_page, > u8 *p =3D vaddr + offset; > =20 > vaddr2 =3D kmap_local_page_try_from_panic(next_page); [Severity: High] This isn't a bug introduced by this patch, but could next_page itself=20 be NULL here? If a 24-bit pixel crosses a page boundary and the next page in the pages=20 array is NULL, passing it into kmap_local_page_try_from_panic() can cause=20 a NULL pointer dereference via PageHighMem(). If CONFIG_HIGHMEM is disabled= ,=20 page_to_virt(NULL) yields a garbage pointer which also crashes upon=20 dereference. This would cause a double fault during a kernel panic,=20 preventing the panic screen from rendering. It looks like similar unchecked page pointers are passed elsewhere in=20 drivers/gpu/drm/drm_panic.c, such as in drm_panic_fill_page(): drm_panic_fill_page() { ... vaddr =3D kmap_local_page_try_from_panic(pages[page]); ... } And in drm_panic_blit_page(), pages[page + 1] is passed without a NULL chec= k=20 even though pages[new_page] is explicitly checked earlier in the function: drm_panic_blit_page() { ... drm_panic_write_pixel24_xpage(vaddr, pages[page + 1], offset, fg32); ... } Would it be safer to verify that next_page and pages[page] are not NULL=20 before attempting to map them, in order to safely handle unmapped or sparse= =20 pages in the display buffer? > + if (!vaddr2) > + return; > =20 > *p++ =3D color & 0xff; > color >>=3D 8; --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20260909085826.6452= 9-1-tzimmermann@suse.de?part=3D2